1. Field of the Invention
The present invention relates to a process cartridge and an image forming apparatus containing the cartridge. The image forming apparatus may be, for example, a laser beam printer, an electrophotographic copying machine, a facsimile machine, a word processor or the like.
2. Related Background Art
In an image forming apparatus such as a printer, a latent image is formed by selectively exposing a photosensitive drum (an image bearing member), which has been uniformly charged. The latent image is then visualized with toner as a toner image, which is in turn, transferred onto a recording sheet, thereby recording an image on the recording sheet. In such an apparatus, wheneven the toner is consumed or used up, new toner must be replenished. However, the toner replenishing operation is not only troublesome, but also often causes the contamination of surroundings. Further, maintenance of various elements of the apparatus must be performed periodically.
To this end, a so-called process cartridge has been proposed and put into practical use (for example, as disclosed in U.S. Pat. Nos. 3,985,436, 4,500,195, 4,540,268 and 4,627,701) wherein a photosensitive drum, a charger, a developing device, a cleaning device and the like are integrally contained in a cartridge housing which can be removably mounted to an image forming apparatus, and whereby the replenishment of toner or the exchange of parts, the service lives of which have expired, can be permitted and maintenance can be facilitated.
By the way, a housing of the process cartridge is constituted by interconnecting a plurality of frames such as a toner frame containing toner, developing frame for supporting a developing device and the like. When the toner frame is integrally joined to the developing frames, both frame made of synthetic resin are welded together by ultrasonic welding, in order to prevent the toner from leaking through the interface between these frames.
In the ultrasonic welding, the frames to be welded are abutted against each other, and the ultrasonic waves are applied to the interface between the frames, thereby welding the frames to each other by heat generated by the ultrasonic waves. However, if the ultrasonic waves are applied to the frames in a condition that the frames are merely abutted against each other, the jointed portion is apt to distort or deform due to the vibration generated by the application of the ultrasonic waves.
In the process cartridge, since various parts such as process means must be attached to the frames, if the frames are deformed, the attaching accuracy for the parts is worsened, and, if a small clearance is generated between the frames due to the deformation thereof, it is feared that the sealing ability is worsened and fine toner particles are leaked through the clearance.